True or False: Kinetic Energy | True or False: Potential Energy | Energy | Thermal Energy | Efficiency and Power |
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What is false?
Kinetic energy depends upon the speed of the object; potential energy depends upon the position of the object.
Kinetic energy is the form of mechanical energy which depends upon the position of an object.
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What is true?
The unit of measurement for potential energy is the Joule.
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What is the Joule?
The unit of energy.
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What is temperature?
Heat is the energy transferred from one object to another because of a difference in ______
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What is input work?
The efficiency of a machine is the ratio of output work to __________.
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What is true?
Kinetic energy depends upon speed. If there is no speed (the object is at rest), then there is no kinetic energy.
If an object is at rest, then it does not have any kinetic energy.
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What is false?
Potential energy has nothing to do with speed; an object could be moving at an elevated position. It is this elevation above zero level which gives an object potential energy.
Moving objects cannot have potential energy.
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What is 300?
Under ideal conditions, if 300 J of work are required to lift a mass to a certain height, the same mass should provide _____ J to do work as it falls back to Earth.
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What is Specific Heat?
The ____ of a substance is the amount of heat needed to raise the temperature of a unit mass of the substance through 1 degree.
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What is less?
In a machine, the output work is always __________ than the input work.
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What is false?
If an object is on the ground, then it does not have potential energy (relative to the ground).
If an object is on the ground, then it does not have any kinetic energy.
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What is true?
As objects free-fall, the height (h) decreases; subsequently, the PE decreases.
Gravitational potential energy is lost as objects free-fall to the ground.
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What is conserved?
Tension does not do work upon the object and so the total mechanical energy is conserved. The presence of air resistance (a non-conservative force) does a little work and so one might notice a very slight change in mechanical energy.
A bowling ball is mounted from a ceiling by way of a strong cable. It is drawn back and released, allowed to swing as a pendulum. As it swings from its highest position to its lowest position, the total mechanical energy is mostly ___________.
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What is Thermal?
The _____ energy content of a swimming pool at a temperature of 20°C is higher than a cup of boiling water.
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What is rate?
Power is the ______ at which work is done.
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What is false?
If an object is falling at a constant velocity (i.e., the air resistance force equals the downward force of gravity), then there is not an increase in kinetic energy.
A falling object always gains kinetic energy as it falls.
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What is true?
The equation states that PEgrav = m•g•h; if the h is doubled, then the PE will be doubled as well.
If the mass of an elevated object is doubled, then its gravitational potential energy will be doubled as well.
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What is 130 J (1.3 x 10^2 J)?
A 6.4 kg bowling ball is lifted 2.1 m onto a storage rack. Calculate the increase in the ball's potential energy?
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What is 14J?
Substance A has twice the specific heat of substance B. Equal amounts of A and B are mixed together. If substance A gains 14 J of heat, substance B loses ____ J of heat.
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What is 3000W?
P = (300 N x 30 m)/3s=3000W
A force of 300 N is used to push a 145 kg mass 30 m in 3 s. Calculate the power developed when pushing the mass.
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What is false?
When it comes to kinetic energy, speed is doubly important (recall v2). So in this case, object A would have more kinetic energy. Doing the calculation yields 2 J for object A and 1 J for object B.
Object A has a mass of 1 kg and a speed of 2 m/s. Object B has a mass of 2 kg and a speed of 1 m/s. Objects A and B have the same kinetic energy.
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What is false?
The final potential energy is calculated as PE = m•g•h = (1 kg)•(~10 m/s/s)•(6 m) = ~60 J; the loss in potential energy during this 4-m fall is -40 J.
A 1-kg object falls from a height of 10 m to a height of 6 m. The final potential energy of the object is approximately 40 J.
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What is 20 m/s?
A 2 kg object initially at rest loses 400 J of potential energy while falling to the ground. Calculate the speed of the object before it strikes the ground.
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What is 3560 J? (3.56 x 10^3J)
Calculate the energy needed to raise the temperature of 185 g of copper from 151°C to 201°C. Copper has a specific heat of 385 J/kg.C°.
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What is 98 J?
eff = WO/WI x 100 90 = 18x9.8.0.5/WI x 100 WI = 98J
A lever is extremely efficient. Using a 90% efficient lever, what input work is required to lift an 18.0 kg mass through a distance of 0.50 m?
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